Coating composition



Patented Oct. 23, 1 934 coa'rmc COMPOSITION William Howard Wright, Schenectady, N. r; n-

Iignor to Schenectady Varnish Company, Inca Schenectady, N. Y.,

a corporation of New York No Drawing. Applioatio May 2,1934, Serial No. 12:, 14

18 Claims.

The present invention relates to varnishes and enamels and particularly those known to the trade as wire ename Wire enamels are usually applied to wire in a continuous operation by passing the wire through a bath of the enamel and then through a baking chamber, where the coating is dried and baked uponthe wire.

Wire, for example, copper wire' so coated, is particularly useful in the electrical arts, i. e. in the manufacture of coils for transformers and motors, the coating being of course insulating.

For the purpose of electrical conductors, the wire is usually given a further coating with an insulating varnish and it is necessary that the 16 wire enamel undercoat be resistant to the solvents used in such superposed insulating coatings, as well as be resistant and inert to the wet varnish of this supplemental coating until the latter has become thoroughly dried and baked out.

ermcre, the wire enamel coating must be resistant to various oils which have a solvent action, such as the cooling oils customarily employed in connection with transformers which frequently reach a high temperature.

Usually the wire enamel is of a type to impart a definite color to the wire. In some cases, a purple, mahogany, or other desired color is obtained, due to the nature of the enamel, the chemical action which takes place between its ingredients, and/or the use of the required baking temperature.

customary in making so-called v It has also been colored enamels, to add a suitable pigment to the enamel to give the desired color such as red,

green, yellow, etc., the pigment being suitably ground and the wire enamel acting as a vehicle.

It will be appreciated, therefore, that the manu-' facture of wire enamels comprehends a number of problems which must be carefully considered- 40 and the present invention briefly stated utilizes a solvent which very materially assists in obtaining a hard, smooth, non-porous and flexible coating thoroughly adherent to the metal wire base and offering a maximum of resistance to the action of solvents and temperature conditions.

The manufacture and use of wire enamels entails specific problems inorder that a. coating of the above desired characteristics will be produced. For example, the constant running of a wire through a bath has a tendency to produce a gelling of the enamel and thereby lower its coating efficiency. This dimculty I find is very considerably relieved by reason of the present invention employing a novel solvent for the enamel,

Also, in the manufacture and use of wire enamels great care must be exercised to prevent formation of bare spots constituting faults, and likewise a uniform coating must be produced. The enamel of the present invention remains sumciently fluid both in the bath and in the baking oven, so that up to the time of final setting of the coating, the composition is fiowable and thereby self-sealing. In other words, the relatively slow evaporative' quality of the coating. and its ability to remain flowable until finally hard- 06 ened in the baking oven, will produce a wire which is free of faults and uniformly coated.

These two very important features of the present invention I have discovered are due primarily to the use of the solvent in the composition of the present invention, .and have resulted in a. marked saving in the cost of material, as well as the cost of manufacture, at the'same time producing a superior product.

As understood in the art, wire enamels are usually. of the oleoresin type including a suitable pigment in the case of the colored enamels, and wherein the oil and resin, which may be or synthetic, are cooked together until so com bined that they will not separate on cooling, '00 whereupon a suitable solvent for the composition is added. v

I have discovered that an excellent solvent for oleoresin bases consistsv of a hydrogenated petroleum oil obtained commercially from the Standard Oil Company of New Jersey. This solvent is invoiced to Schenectady Varnish Company, Inc. as Hydrosolvent and at present numbered in accordance with the boiling range. v

This product, I am informed by the Standard Oil Company of New Jersey, is produced in accordance with processes typified by United States patents to Krauch, No. 1,890,434, Dec; 6, 1932, and Pier et al., No. 1,910,050, May 23, 1933, being representative of certain United States and foreign patents owned jointly by it and the I. G. Dye Trust'of Germany. Furthermore, I am advised by the Standard Oil Company of New Jersey that this hydrogenated petroleum oil which I utilize as a solvent is a hydrogenation fraction boiling 1 up to 600 F. and is made from a petroleum base. This product is made by the hydrogenation of crude petroleum oils, 'distillates thereof, cracked petroleum products and other petroleum oils,

either crude or in various states of refinement, by

the use of high pressure and temperature with or without a catalyst.

:The hydrogenation may be carried on to any desired extent, that is, the saturation with hydrogen, and I am also informed that "Hy'drosolvent No. 3 and HydrosolventNo. 4, representative of the products manufactured by said Standard Oil Company of New Jersey, have boiling ranges of 365-420" and 420-550 F., respectively, and that similarly produced solvents having a higher or lower boiling range up to 600 F., for example ZOO-600 F., may be made by the process covered in the patents and patent applications above mentioned.

I prefer to use a solvent having a boiling range of between 250 F. and 300 F. to 000 F. In some cases, particularly where the wire is of very thin gauge, a solvent having a boiling range of about 200 F. to 600 F. has been found desirable.

I also have, discovered that the use of this hydrogenated solvent obtained from petroleum permits more complete oxidation and chemical action of the varnish in the baking chamber and that I secure a hard, permanent, and of particular importance, a non-porous film.

Aside from possessing excellent solvent characteristics whereby a film of optimum efficiency is obtained, the hydrogenated petroleum oil solvent is relatively non-evaporative and does not give oif fumes which are'of the same nature as coal tar derivatives, i. e. benzol or coal tar naphtha, which have a very toxic effect upon the workmen and a very irritating eifect on the eyes, nose and throat. The coating prepared with the present solvent on the other hand permits the workmen to operate comfortably with little or no irritation or ill effects.

Furthermore, I find that the use of a solvent of this character is an improvement over the usual coal tar derivative solvents, in that it maintains the stability of the varnish or enamel more acceptably in the usual enameling machines and in the circulating systems used by the large manufacturers to feed these machines. That is to say, the solvent which I have discovered, is

effective in maintaining the varnish or enamel free of gelling in the bath and circulating systems, and also in maintaining the coating stable after it has been applied upon the wire before introduction .into the usual baking chamber. This will be appreciated, since the solvent is relatively non-evaporative. Asstated, the baking of the varnish or enamel takes place at a relatively high temperature and results in a hard, smooth, non-porous and flexible coating thoroughly adherent to the metal base wire.

These various advantages are of particular importance, since I have observed the toxic conditions surrounding the use of coal tar derivatives such as coal tar naphtha, wherein the fumes affect the nose and throat and eyes of the workmen in the enameling room. Furthermore, these coal tar derivatives are not capable of producing the same stability to maintain the varnish constantly in working condition during the various steps leading to the production of the final product. That is, the constantoirculation of the enamel or the constant running of the pulleys ,in the bath over which the wire moves, tends to gell the enamel. With coal tar derivatives this takes place in a relatively short time. The presentenamel, however, which includes a hydrogenated petroleum product as above set forth, is relatively non-gelling.

In carrying out the present invention, I employ an oil, preferably a vegetable drying oil, or a combination of drying oils.

By drying 1 oils, I mean linseed oil, tung oil or perillaoil. In addition, I use in some cases a semi-drying oil such as soya bean oil or fish oil or a non-drying 011,.

'such as castor oil. These are used alone or suitably combined. The drying and semi-drying oils are glycerol esters of unsaturated organic acids and hence take up omen and harden.

The resin employed may be a natural one, for example, kauri, or one of the copals. Also, I employ synthetic resins of the cumaron type, the aldehyde condensation product type such as bakelite or the ;glyptal type, i. e. resins produced from glycerol and organic acids.

Both the resins and theoils are well known commercial products and they or their equivalents have been used in' the manufacture of varnishes and enamels, so that a specific description of them is not deemed necessary for one skilled in the art.

The resin is melted in the usual manner and while in heated condition and fluid, the oil which has previously been heated or blown in another receptacle is added. The oil and resin are cooked together until they are so combined'that they will not separate on cooling. Thereupon a suitbase is dissolved therein. I find that this solvent 100 acts to promote the even dispersion of the base and enhances the flow of the varnish or enamel, since it is relatively non-evaporative and resists gelling. Moreover, and because of these stabiliz- 'ing characteristics, the varnish is maintained in good working condition and stable in the varnish machines whereby an even coating is applied to the metal wire and which, upon subsequent baking, forms a smooth, hard, but flexible, impervious film. In baking the coated wire, the enamel of the present invention remains stable and fluid until finally set. That is to say, its non-evapora- 'tive tendency keeps the enamel from becoming preliminarily hard and porous. The result is then that the enamel is fluid upon the wire in the baking chamber and any potential cracks or gaps in the coating are in effect. self-sealed by reason of this continuing fluidity and-a smooth continuous coating is produced. The evaporation as explained is gradual, permitting this result and 1 assuring a final. smooth, non-porous, insulating fllm I some cases, the varnish or enamel will so react, either due to chemical action and/or the presence of the baking temperature, as to produce 5 a definite color or shade. Thus, for example, I obtain a mahogany color or a purple color without the use of pigments. & P On the other hand, the trade has indicated a 'desire "for colored enamels and I, therefore, grind. the proper pigmentausing the wire enamel as a vehicle, and in which th pigment is dispersed, in some cases.

The proportions of oil, resin and solvent, of

course, will vary with the particular composition being treated, and I make both long and short varnishes and enamels. I use the hydrogenated. petroleum solvent alone as the solvent for the oleoresin base or I use mixtures 'of this solvent, for example, with no coal tar naphtha or with a non-hydrogenated petroleum product such as kerosene. The percentage mixtures of the two solvents will be determined by the character of the base.

The hydrogenated petroleum solvent is relativelyheavy, as will be observed, having a boil- -ing range up to 600 F. and usually of approximately 300-600" F., and I find this of advantage in that notonly is the evaporation retarded in the enameling room whereby the' condition 1,977,: the varnish is maintained at optimum emciency,

but, moreover, the vapors are not toxic to the eyes, nose and throat of the workmen as is; true of present day solvents derived from coal tar.

In the case where the solvent has lower boiling ranges below 300 F. as above mentioned, as for example, 200 F., 250 F., or 275 F. to 600 It, the solvent exhibits a similar non-gelling action and self-sealing qualities. The conditions entering into the manufacture of the enamel and its application to the wire are controlled depending upon the nature oi the wire, as for example the metal of which it is composed, the gauge of the wire, and the final product desired.

It is to be understood that in reierring to the hydrogenated petroleum oil as a varnish or enamel solvent, I mean as well that it has the function of a thinner or diluent.

The varnish is applied to wire, such as copper wire, aluminum wire, nichrome wire, and steel wire, or any other metal wire in a continuous process. That is, the bare wire is on a spool and is run continuously throughthe bath oi enamel and into and through a heating chamber of varying length and the final coated product drawn from the heating chamber is then wound upon another spool. The passage of the wire through the bath and through the heating chamber is controlled, so as to insure a thorough coating and a thorough baking respectively. The baking temperature is usually from 400 to 900 F. In some cases temperatures below 400 F. may be used.

The wire removed from the heating chamber and the varnish composition thereon will be found to be chemically changed and completely oxidized into a smooth, hard insulating film thoroughly adherent to the metal wire base and, of particular importance, flexible and free from' porosity.

A careful examination of the final coating discloses that it possesses novel characteristics-as regards adherency to the metal, and particularly as to smoothness, hardness and flexibility. Also, the coating is resistant to the action of solvents and varnishes which are subsequently applied over the coated wire and baked thereon for insulating purposes. Moreover, the coating is oil a charactor to be resistant to temperature changes in use and does not break down in the presence of lubricating oils and cooling liquids under the varying temperature conditions prevailing, for example, where a coil of the wire is used with a transformer.

It will be understood that I will, in some cases, combine or mix various of the solvents mentioned to produce a blended solvent; also, that the several solvents he the boiling ranges specified may or may not be of uniform boiling range, and in some cases consist of fractions boiling at the lower ranges specified, as well as fractions which boil at the high ranges.

As stated, I make a clear va which, upon bg, presents a coating having a suitably colored shade, clilferent from that oil the original varnish, or 'I add to the varnish a suitable pig ment for the purpose of produclnga desired color. I find that my improved solvent acts to bring out the color very efiectively in the clear v; and is inert with respect to the usual ground pigments.

I attribute the very eflicient results obtained with thewire enamel or this invention to the. advantageous/use of the new hydro'genated'solvent which, in addition to removingtoxic conditions in the manufacturing operation, has the equally lmportantadvantage of materially enhancing the ilnal coating produced upon the wire.

This application is a continuation in part of my co-pending application, Serial No. 689,677, flled Sept. 15, 1933. p

I claim: v

l. A wire enamel comprisinga drying oil, a resin, and a solvent comprising a hydrogenated petroleum product, which is a hydrogenation traction boiling from substantially 200 F. to 600 F.

2. A wire enamel comprising a drying oil, a resin, and a solvent comprising ,a hydrogenated petroleum product, which is a hydrogenation traction boiling from substantially 200 F. to 600 F., and anon-hydrogenated solvent.

3. As an article 01' manufacture, metal wire having baked thereon a wire enamel comprising a drying oil, a resin, and a solvent comprising a hydrogenated petroleum product which is a hydrogenation fraction boiling from substantially 200 F. to 600 F., said enamel being resistant. to the action of solvents contained in supplemental insulating coatings vand to temperatures employed to bake such insulating coatings over the enamel.

4. The process oi coating wire which consists in providing a bath of enamel containing a solvent which is a hydrogenated petroleum product boiling between substantially 200 F and 600 F. and which throughout the existence of the bath remains substantially non-evaporative whereby there is provided a substantially permanently non-gelling bath resistant to agitation as occasioned by the continuous passage of a wire length or lengths therethrough, continuously conducting a length or wire through said bath and forming a coating thereon, and setting the coating by subjecting the same to a baking action.

5. A wire enamel comprising a drying oil, .a resin, and a solvent comprising a hydrogenated petroleum product, which is a hydrogenation rdrogenation fraction boiling from substantially 2604755 1". to 600 E, said enamel being resistant to the action of solvents contained in supplemental insulating coatings and to temperatures employed to bake such insulating coatings over the enamel.

0. The process of coating wire which consists, in providing a bath of enamel containing a solvent which is a hydrogenated'petroleum product be between substantially 250-2'75 F. to 600 F. and which throughout the existence of the bath remains substantially non-evaporative whereby there is provided a substantially permanent non-ge bath resistant to agitation as occasioned by the continuous passage of a wire t 1 or lengths therethroush, continuously conducting a length or wire through said bath 140 and iorming a ting thereon, and setting the coating by subjecting the same to-a baking action.

0. A wire enamel comprising a drying oil, a resin, and a solvent comprising a hydrogenated petroleum product, which is a hydrogenation 1N 4 fraction boiling iro'm substantially 3p0'-F:-, to 600 F. v 10. A wire enamel comprising a drying oil, a

resin, and a solvent comprising a -hydrogenated "petroleum product, which is .a 'hydrogenation fraction boiling from-substantially 300 I". to 600 F., and a non-hydrogenated solventi,

' 11.'As an arose of manufacture, metal wire having baked thereon a wire enamel comprising a drying oil, a-resin, and a solvent comprising a hydrogenated petroleumproduct which is a hydrogenation fraction boiling rrd'm' substantially 300 F. to 600 F., said enamel being resistant to the action of solvents contained in'supplemental' insulating coatings and' to temperatures employed to bake such insulatingcoatings over the enamel. 3' 12. The process of coating wire which consists in-providing a bath ofenamel containinga'sol yentwhich is a hydrogenated petroleum product boiling between substantially 300 F. and 600 F.

. aiiii which throughout the existence of the bath drogenation traction -boiling irom substantially 20091 to 600 F., and a non-hydrogenated 'solvent, said enamel being resistant to the action of solvents contained in supplemental insulating coatings and to temperatures employed to bake such insulating coatings over the enamel l a 14. As an article of manufacture, metal wire having baked thereon'a wire enamel comprising a drying oil, a resin, and a solvent comprising a hydrogenated petroleum product which is a hydrogenation traction boiling from substantially 250275 F. to 600? It, andjva non-hydrogenated solvent, said enamel being resistant to the action of solvents contained in supplemental insu-g lating coatings and to temperatures employedto bake such insulating coatings over the enamel.

15. As an article fof manufacture, metal wire having baked thereon a wire enamel'comprising adrying-.'oil,.a reslmand asolvent comprising a e. hydrogenatedpetroleumproduct which .is a hybath resistant to agitation asoccasioned by the continuous passageof a'wire length or lengths therethrough, continuously conducting a length oi-wire through said bath' and forming a coating thereon, and setting the coatingby subjecting the same to a baking action. j

17; The process of 7 coating wire which consists in providing a bath of enamel containing? solvent whichfisa hydrogenated petroleum product boiling between substantially 250-2'75-"-F'; to 600 F.; and a nonhydrogenated solvent, which throughout the existence-oi the mar mains "substantially non-evaporative whereby there is'-provided"a substantially permanent nongelling bath resistant to agitation as occasioned by the continuous passagevoi a\vire-lei1gth gn lengths therethrough, continuously conducting a length of wire through said bath and forming a jecting the same to a baking action. c

18. The process 0! coat wirewhich consists in providing a bath of enamel containing a sol: vent which is a hydrogenated petroleum product coating'thereon', and setting the coatingbysub boilingbetween substantially 300-F. and 000 and; a non-hydrogenated solvent, and which throughouttheexistence oi the bath remains sub-j stantially nonevaporative whereby there is pro:

vided a substantially non-gelling bath resistant to agitation as occasioned by the continuous passage of a ,wire length or lengths therethrough,

continuously conducting a length of wire through said bath andiorming a coating there- 'on and setting the coating by subjecting the same to a baking action.

" wnmaiu .nowsan wnIGH'r. 

